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Genitofemoral nerve

The genitofemoral nerve is a mixed sensory and motor nerve derived from the lumbar plexus. It arises from the anterior rami of L1 and L2 spinal nerves. It pierces the psoas major muscle and runs down its anterior surface before dividing into two terminal branches: the genital branch and the femoral branch. It plays a key role in supplying sensation to the upper anterior thigh and motor fibers to the cremaster muscle in males.

This nerve is clinically relevant in groin pain syndromes, hernia repair surgeries, and can be affected by entrapment or trauma.

Synonyms

  • Nervus genitofemoralis

  • External spermatic nerve (genital branch, historical term)

  • Lumbar plexus branch L1–L2

Origin, Course, and Branches

  • Origin: Arises from the lumbar plexus, formed by anterior rami of L1–L2 spinal nerves

  • Course:

    • Emerges within the substance of the psoas major muscle

    • Descends along the anterior surface of the psoas major

    • Divides above the inguinal ligament into genital and femoral branches

  • Branches:

    • Genital branch: Enters the inguinal canal via the deep inguinal ring

      • In males: supplies motor fibers to the cremaster muscle and sensory fibers to the scrotum

      • In females: supplies sensation to the mons pubis and labia majora

    • Femoral branch: Passes beneath the inguinal ligament to supply sensation to the skin over the femoral triangle of the upper anterior thigh

Relations

  • Lies anterior to the psoas major muscle

  • Medially related to the common iliac vessels and ureter

  • Laterally related to the iliacus muscle and femoral nerve

  • Inferiorly related to the inguinal ligament and spermatic cord/round ligament

Function

  • Sensory:

    • Genital branch: sensation to scrotum (male) or mons pubis/labia majora (female)

    • Femoral branch: sensation to skin of upper anterior thigh

  • Motor:

    • Genital branch supplies the cremaster muscle in males

  • Reflex:

    • Mediates the afferent and efferent limbs of the cremasteric reflex in males

Clinical Significance

  • May be injured during inguinal hernia repair or abdominal surgeries

  • Entrapment causes chronic groin pain or neuropathy

  • Important landmark in laparoscopic and open groin procedures

  • Target for nerve blocks in anesthesia and pain management

MRI Appearance

T1-weighted images:

  • Nerve appears as a thin linear low-to-intermediate signal intensity structure against bright fat planes

T2-weighted images:

  • Nerve shows intermediate to mildly hyperintense signal relative to muscle

  • Pathological nerves (inflammation, entrapment) may appear bright

STIR (Short Tau Inversion Recovery):

  • Normal nerve shows low signal

  • Inflamed or edematous nerve shows bright hyperintensity

T1 Fat-Sat Post-Contrast:

  • Normal nerve enhances minimally

  • Pathologic nerve shows focal or diffuse enhancement (neuritis, tumor, infection)

3D T2 SPACE / CISS:

  • Nerve appears as a intermediate to mildly hyperintense signal linear structure surrounded by bright CSF or fat

  • Provides excellent contrast for tracing the nerve course within complex anatomical regions

  • Useful for detecting small lesions, entrapment, or compression

CT Appearance

Non-Contrast CT:

  • Nerve not directly visualized; inferred as a thin soft tissue structure within fat planes of retroperitoneum and groin

  • Surrounding fat helps localize its course along psoas major and inguinal region

Post-Contrast CT:

  • Nerve itself shows no significant enhancement

  • Pathological conditions (tumors, inflammatory infiltration) may appear as soft tissue thickening or enhancing masses along its course

MRI image

Genitofemoral nerve

MRI image

Genitofemoral nerve mri axial image